1. Field of the Invention
The present invention relates to a magnetic head for magnetic tapes, and more specifically to a magnetic head for computer tapes which has superior tape-to-head contact stability.
2. Description of Related Art
With a recent dramatic increases in amounts of information, there has been more demand for increases in the density and the capacity of magnetic tapes serving as a data storage medium. Possible methods for increasing the capacity of magnetic tapes are, for example: increasing a tape length per roll by reducing the total thickness of the tape; increasing the recording density in the longitudinal direction of the tape by reducing the recording wavelength; and increasing the recording density in the width direction of the tape by reducing the recording track width (increasing the recording density of the magnetic tape).
Moreover, magnetoresistance effect heads (MR heads) utilizing a magnetoresistance effect element (MR element) having high sensitivity are being used as magnetic heads in order to implement such an increase in the recording density of magnetic tapes. When a further increase in the capacity is to be achieved by making full use of these techniques, a head contact stabilizing technique for maintaining stable high reproduction output by reducing the spacing at the point of contact between the moving magnetic tape and the head is important. In the field of data storage, use of linear recording magnetic tape apparatuses is widespread, and MR heads equipped with a MR element, such as described above, are employed.
FIGS. 3A and 3B show cross sections of examples of a conventional magnetic head (MR head). The magnetic head 11 shown in FIG. 3A and the magnetic head 11 shown in FIG. 3B have different sliding surfaces, i.e., a curved surface or a flat surface, but otherwise have the same configuration. The magnetic head 11 includes a sliding surface 13 that comes in contact with a moving magnetic tape 12. The sliding surface 13 includes an electromagnetic transducing element 14. Edges 15 are formed at each end of the sliding surface 13. The magnetic tape 12 moves while being wrapped around the magnetic head 11 so as to form an angle θ with respect to a tangent to the sliding surface 13.
FIGS. 4A and 4B are diagrams for illustrating head contact of the magnetic head 11 having the configuration shown in FIGS. 3A and 3B. FIG. 4A is a diagram showing how air flows in the vicinity of the magnetic head 11, and FIG. 4B is a graph showing how the air pressure P varies along the direction of movement of the magnetic tape 12.
The magnetic tape 12 is strongly pressed against the sliding surface 13 by tape tension. Thus, the flow of entrained air 16 to the sliding surface 13 is cut off at the edge 15 on the upstream side (left side). Also, the flow of entrained air 17 to the sliding surface 13 is cut off at the edge 15 on the downstream side (right side). As a result, a state of negative pressure is created in the space between the magnetic tape 12 and the sliding surface 13, as shown in FIG. 4B.
Therefore, the magnetic tape 12 moves while being drawn to the sliding surface 13. Consequently, the spacing between the electromagnetic transducing element 14 and the magnetic layer becomes small, thus ensuring head contact.
In order to ensure stable head contact, it is important to control the wrap angle θ within a preferred range according to the modulus of elasticity, the thickness, and the tension during movement of a magnetic tape. For this purpose, there have been proposed, for example, a method of providing guides called “outriggers” on the upstream side and the downstream side of a magnetic head so as to keep the wrap angle constant (U.S. Pat. No. 5,905,613), a method of controlling the dimensions of a groove between an outrigger and a sliding surface (JP 2002-183906A), a method of providing a slot around a sliding surface (JP 2004-342303A), and a method of providing a cavity in a central portion of a sliding surface (JP 2000-207800A).
FIG. 5 shows a cross-sectional view of an example of a configuration in which a magnetic head includes fixed guides (outriggers). In this configuration, fixed guides 18 are added on each side of the magnetic head 11. As a result, the wrap angle θ of a magnetic tape 12 during movement is stably kept constant.
Generally, the ability to read data from the latest three generations of magnetic tapes is standard in data storage drives for use in computers. In this situation, it is required that data on different generations of tapes having different thicknesses (usually, a tape thickness has decreased with each generation) be read correctly using the same drive.
However, in a conventional magnetic head as described above, the head is designed for a specific bending stiffness of the magnetic tape. Thus, head contact varies from generation to generation of magnetic tapes, and it has been difficult to sustain favorable head contact with magnetic tapes of all thicknesses used.
Usually, magnetic heads wear upon contact with a magnetic tape, so that the head contour changes gradually. Continued use of magnetic tapes having the same thickness initially causes the head contour to change such that the magnetic tapes conform to the head and the head contact stability improves, but subsequently results in gradual deterioration in the output.
In particular, when a thick tape is moved across a head worn down by thin tapes, it is difficult for the thick tape to follow the contour worn down by the thin tapes, and thus there is a problem in that head contact becomes poor.